1. How to separate On-Account Invoice number sequence from Original Invoice number

We need to book an Accrued revenue for partially completed projects. We are using on-account transaction for transaction type prepayment journal voucher in Time & Material project to record accrued revenue & post it from Invoice Proposal to effect it in our accrued sales revenue account.At the time of actual invoicing to the customer First we are reversing On-Account accrued revenue by selecting Credit note & posting it from Invoice Proposal. Then Post posting the actual invoice from Invoice ProposalMy question is whenever I am passing the entry for on-account transaction, system is not generating the number sequence from On-Account invoice nor Credit note from On-Account Credit Invoice. But generating it from original Invoice number sequence.Can you please let me know how can we separate On-Account invoice number sequence from original invoice number sequence